Method and device for recovering heat from intermittently and briefly released blow-off steam charge

ABSTRACT

The invention relates to a method for recovering heat from intermittently and instantaneously released blow-off steam charges. The method is carried out using a container ( 6 ) with an internal volume ( 2 ), provided with an inlet ( 7 ) and an outlet ( 10 ). The method comprises the steps of supplying a blow-off steam charge (Sh) via the inlet ( 7 ) to the container ( 6 ) and collecting the latter in the internal volume ( 2 ) of the container. In this case, the charge (Sh) may be held in a gravitational field. It is possible to recover energy from a portion of the blow-off steam charge (Sh) by condensation thereof. The condensation results in a stream from said portion to an outlet ( 10 ) which is at a lower gravitational potential. Via the outlet ( 10 ), it is possible to discharge a portion of the charge (Sh) from the internal volume ( 2 ) of the container ( 6 ) at a lower gravitational potential. This can be effected by supplying a subsequent blow-off steam charge (Sh) to the internal volume ( 2 ), thereby expelling the charge (Sh) which is present via the outlet ( 10 ). During heat recovery air is drawn in via the outlet ( 10 ).

The invention relates to a method for recovering heat from blow-offsteam, wherein the method is carried out using a container with aninternal volume, provided with an inlet and an outlet.

The invention also relates to a device for recovering heat from blow-offsteam.

The intermittent and brief release of blow-off steam occurs with asteam-peeling device. The steam-peeling device can be used for peelingcrops, in particular for peeling tuberous crops, such as for examplepotatoes. To this end, an amount of steam at a pressure of 15-17 bars isintroduced into a container containing the crops to be peeled. For aperiod of 20 to 25 seconds, the crops are subjected to the steam. Thenthe device is opened in order to allow the steam to escape and thepressure is taken off the device. As a result thereof, the skin comesoff the tuberous crop and will partly be carried along with the steam,thus achieving the desired peeling effect. The steam is released forapproximately 2 to 3 seconds. The total cycle time is approximately60-70 seconds.

A method and device for recovering heat from this intermittently andbriefly released blow-off steam are known. The known device makes use ofa vessel which is provided at the bottom with an inlet for steam. Thevessel is provided with a condenser, such as for example a system ofceramic or stainless steel packed beds. In addition, the vessel isprovided with a water circuit, in which water flows over the condenserfrom an upper side of the vessel. On a lower side of the vessel, thewater is collected and re-introduced to an upper side of the vessel viaa heat exchanger which is situated outside the vessel.

Passing the steam through beds ensures that the steam transfers its heatto the beds, as a result of which the heat is stored in the bufferstack. By then passing water via the condenser, it is possible torecover heat. The heat exchanger transfers the heat absorbed by thewater to another liquid, depending on the requirements.

It is a drawback of the known method and device that the buffer materialis soiled relatively quickly as a result of, for example, peelings, andis also relatively difficult to clean. Due to the fact that the peelingsof the various tuberous crops are partly carried along with the steam,they will also end up in the heat-recovery device. Here, they will bedeposited on the condenser, and possibly also in the heat exchanger. Inaddition, the recirculated water in the water circuit is soiled.Cleaning such a device takes a lot of time, as a result of which thedevice cannot be used for extended periods of time.

It is therefore an object of the invention to provide a method and adevice by means of which at least one of said problems of the knowndevice is at least partly solved or alleviated.

To this end, the invention provides a method for recovering heat fromintermittently and instantaneously released blow-off steam charges,wherein the method is carried out using a container with an internalvolume, provided with an inlet and an outlet, wherein the methodcomprises the following steps:

-   -   supplying to the container via the inlet and collecting in the        internal volume of the container a blow-off steam charge,        wherein the charge is held in a gravitational field;    -   recovering energy from a portion of the blow-off steam charge by        condensation thereof, wherein condensation results in a stream        from said portion to an outlet which is at a lower gravitational        potential;    -   discharging a portion of the charge from the internal volume of        the container via the outlet at a lower gravitational potential        by supplying a subsequent blow-off steam charge to the internal        volume and thus expelling the charge which is present via the        outlet;    -   drawing in air via the outlet during heat recovery.

The method is carried out using a container with an internal volume. Thecontainer may be an open container. An inlet is connected to theinternal volume for supplying the charge to said internal volume. Also,an outlet is provided via which a portion of the charge of steam duringthe condensation is replaced by air. The blow-off steam charge iscollected inside the container and is thus brought into a gravitationalfield.

The method according to the present invention comprises recoveringenergy in the container and in particular heat from at least a portionof the blow-off steam charge. The terms energy recovery and heatrecovery will be used interchangeably in this application. Heat exchangemay take place. As a result of the heat exchange, at least a portion ofthe steam charge can condense as well. The energy which is releasedduring condensation can be collected in another medium by means of heatexchange. In another embodiment energy is recovered according to themethod from the fact that the condensation of the steam charge is usedto heat another medium, for example recirculated water.

The method according to the present invention comprises the step ofrecovering energy from a portion of the blow-off steam charge at alocation which is at a higher gravitational potential with respect tothe outlet. The outlet is situated lower than the location where energyrecovery takes place. The inlet for replacement air may also be at alower location. In the present invention, the term gravitationalpotential is intended to mean the amount of energy which is present inthe blow-off steam charge due to the location of the object in thegravitational field. It is a measure for the potential energy ofportions of the charge as a result of the gravitational field. Heatexchange results in the blow-off steam charge cooling down and/orcondensing, as a result of which the density increases and/or the steampasses to the liquid phase, and thus drops to the lower potential. Thisresults in a stream in the direction of the outlet at the lowerpotential. Recovering heat from a portion of the steam charge ensuresthat said portion either becomes liquid (transition to liquid phase) orattains a higher density, as a result of which a downward stream willtake place in the direction of the outlet. In this way, aself-separating capacity is created in the container. The portion of thecharge from which heat is recovered will flow away from the locationwhere heat recovery takes place and is replaced by a portion of thecharge from which no or less heat has been recovered. It is alsopossible for air to be drawn into the container due to the significantchange in volume of the steam when it passes to a liquid phase. Theportion of the charge from which heat has been recovered, will bereferred to below as ‘fluid’, as it may be a combination of liquid andgas.

The method according to the present invention furthermore comprises thestep of discharging the fluids present in the internal volume of thecontainer via the outlet at a lower gravitational potential. Both gasand liquid, remainders of the supplied charge, are passed via a lowerpotential in order to leave the internal volume. According to themethod, a new charge of steam is supplied. The supply of the new chargeresults in the gasses present in the internal volume being displaced.Due to the above-described self-separating capacity, the fluids fromwhich the least heat can be recovered/the most heat has already beenrecovered, are at the lower gravitational potential and thus nearer theoutlet. Precisely this portion will be discharged first by displacement.In this way, a kind of first-in-first-out system is obtained in which asteam charge is introduced, self-separation takes place where colderportions/condensed portions move to the lower potential, and where thesupply of a new charge results in the displacement of the volume whichis present with said colder portions leaving the internal volume via theoutlet first.

The method according to the present invention makes it possible torecover heat in a relatively continuous manner from an intermittentlyand instantaneously released blow-off steam charge. The batchwiseprocess of releasing the blow-off steam charges is thus turned into arelatively continuous process. As a result thereof, it is now possibleto recover heat from the blow-off steam charge in a more efficientmanner.

The method according to the present invention comprises the step ofdrawing in air via the outlet while recovering heat. In this case, theoutlet allows gas/air to be drawn into the internal volume. During heatrecovery and in particular during the condensation of the steam charge,a volume reduction takes place which is compensated for by drawing inair via the outlet. This also results in cold air, in particular outsideair, being sucked in via an open connection of the outlet. Due to thefact that the steam is at a higher gravitational potential due to thelower density, there is very little, if any, heat exchange with thesupplied cold air and the self-induced separation remains in force.

The outlet is in particular an open outlet, in particular a pipe orflue, the opening of which is at a lower potential than where heatrecovery takes place, and in which said opening is placed preferably inthe centre of the volume. In an embodiment, an open container is used,for example a hat-like container. A large portion of a bottom side maybe open. Steam remains trapped under the hat.

In an embodiment of the method, it is furthermore advantageous toprovide an internal volume above the entrance to the outlet, i.e. at ahigher potential than the outlet, which volume is greater than thevolume of the supplied blow-off steam charge. When the charge issupplied, the old charge/fluid which is present will be displaced in thedirection of the outlet and be forced out. The new charge, hot andtherefore having a low density, forms a kind of pusher or sucker whichforces the colder fluid out via the outlet. As the internal volume abovethe outlet is greater than the volume of the supplied charge, thesupplied charge will not reach the outlet, thus making it possible toeffect a complete heat exchange. The container thus forms a buffer whichmakes it possible to recover heat for a relatively long time from ablow-off steam charge which was instantaneously introduced into thecontainer. The method according to the invention thus comprisesbuffering the blow-off steam charge in the internal volume. This is afurther step in rendering the batch process continuous.

In an embodiment of the method, the volume of the supplied blow-offsteam charge is between 70% and 90% of the internal volume of thecontainer. The container is overdimensioned, as it were, and comprises alarger internal volume than the volume of the supplied charge. In thisway, no portion of the supplied charge is wasted, and heat can berecovered in a relatively efficient manner. Due to the fact that thecontainer is overdimensioned, it is possible to provide a buffer ofblow-off steam in the container. Thus, heat can be recovered for arelatively long time from a blow-off steam charge which was introducedinstantaneously into the container.

It is possible for the step of exchanging heat from the blow-off steamcharge to at least partly coincide with the step of supplying the nextblow-off steam charge. In this way, it is possible to continuouslyrecover heat from the intermittently and instantaneously releasedblow-off steam charges. Thus, there will be no periods during which noheat can be recovered.

It is possible for the step of recovering heat from the blow-off steamto comprise bringing the blow-off steam into contact with a heatexchanger provided in the container. The heat exchanger may be providedwith a transportation medium, such as for example water. The water mayhave an inlet temperature of approximately 80° C., and an outlettemperature of approximately 95° C. However, other inlet temperaturesare also conceivable. In particular, the outlet temperature is adaptedto the condensation temperature of steam. It will be clear to the personskilled in the art that, depending on the demands he makes, the heatexchanger can be dimensioned in any desired way, so that a certainoutlet temperature is achieved and/or inlet temperature can be used. Itis also possible to use different flow rates for the transfer medium inthe heat exchanger.

A steam/air layer may be formed in the container. The steam may besituated at the top side of the steam/air layer, while the air is at thebottom side of the steam/air layer. The density of air is greater thanthe density of steam. In this way, a two-layered system is formed in thecontainer. The steam and air form a latent layer in the container. Thesteam is situated at the top side of the container. After the energyfrom the steam has been transferred, relatively cold air can collect inthe bottom portion of the container, for example by being drawn in viathe outlet or another entrance. The steam layer floats on the air layer,as it were. A portion of the steam may be brought into heat-exchangingcontact with the heat exchanger.

In an embodiment, the steam/air layer is situated near the heatexchanger after the introduction of a blow-off steam charge. Byexchanging heat, it is possible for steam to condense. This will resultin a reduction in the steam layer and cause the boundary of thesteam/air layer to move in the direction of the heat exchanger. It isadvantageous if the boundary of the steam/air layer is always under(lower gravitational potential) the location of the energy recovery/heatexchange. This distance is smallest just before the step of supplyingthe next charge. Due to the fact that the boundary of the steam/airlayer is still at a vertical distance from the heat exchanger, the heatexchanger will be in heat-exchanging contact with the steam, at thepoint in time when a new charge is supplied. In this way, heat can berecovered continuously from the intermittently and instantaneouslyreleased blow-off steam charges.

After the new charge has been supplied, the boundary of the steam/airlayer is situated above the outlet. Consequently, steam will not leavethe internal volume via the outlet immediately after having beensupplied.

The height difference between the steam/air layer after the introductionand before the supply corresponds to a buffer volume of blow-off steamin the container. The buffer volume is used to bridge the periods whenno steam charge is released, so that heat can be recovered in arelatively continuous manner. The buffer volume is partly dependent onthe volume of blow-off steam charge, the time period during which heatcan be recovered from the total volume of blow-off steam, and the timeperiod between the release of two successive blow-off steam charges.Other variables, such as the efficiency of the heat exchanger and thedimensions of the container, may also affect the buffer volume.

In an embodiment of the method, the buffer volume is between 10 m³ and30 m³.

It is possible for the heat recovery to take place in a heat-exchangingvolume, wherein the heat-exchanging volume is between 10% and 30% of thevolume of the blow-off steam charge, and wherein the remaining portionof the blow-off steam charge forms the buffer volume.

It is also possible that the step of supplying the next blow-off steamcharge results in a boundary layer between the blow-off steam chargewhich is already present and the next blow-off steam charge, with theboundary layer being situated near the outlet of the container after thesupply step. In this manner, a portion, preferably the largest portion,of the charge which is already present is forced out of the container.Another portion remains behind in the container. This latter portion isrelatively cold and will collect at a lower gravitational potential,preferably near the outlet. Heie, it forms a barrier between the newlysupplied blow-off steam charge and the discharge thereof from theinternal volume of the container. In this way, the relatively hot andnewly supplied blow-off steam charge is kept in the container in aneffective manner. The newly supplied blow-off steam charge cannot leavethe container, or at least only with relatively great difficulty, as aresult of which the energy losses are relatively small.

It is advantageous if the blow-off steam charge is supplied at a topside of the container. The blow-off steam can be discharged via a bottomside of the container. Such an embodiment of the method is relativelyefficient. The relatively hot blow-off steam is supplied at a top side,in which case heat is recovered at a top side as well. Discharging viathe bottom side ensures that the blow-off steam has to go via a lowergravitational potential. The outlet is also situated in a location towhich the cooled-down blow-off steam tends to flow after it hasundergone heat exchange. Consequently, the charges can hardly exchangeheat with one another, as a result of which relatively little heat islost.

In an embodiment, the supply of blow-off steam takes place during afirst time period. Heat recovery from the blow-off steam takes placeduring a second time period. Preferably, the first time period is lessthan 5% of the second time period. Supplying the blow-off steam chargemay, for example, last 2 to 3 seconds. The cycle time, i.e. the timebetween two consecutive blow-off steam charges, is approximately 60 to70 seconds. Preferably, heat is recovered from the blow-off steam for alarge part of the cycle time. In this way, the time which is availablebetween two consecutive blow-off steam charges can be used efficientlyto recover heat from the blow-off steam charge. By using a large part ofthe cycle time, it also becomes possible to achieve a relativelycontinuous heat recovery.

In an embodiment of the method, the blow-off steam is supplied to thevessel in a tangential direction. It is also possible to introduce theblow-off steam radially into the vessel. In this case, the container canhave a round cross section. The radial introduction ensures that theblow-off steam is kept in that part of the container into which theblow-off steam is introduced. When the blow-off steam is introduced, forexample into the top portion of the container, the blow-off steam willalso stay in this top portion. This is particularly advantageous when aheat exchanger is provided in the top part of the container. Inaddition, the tangential introduction will ensure that the blow-offsteam will be mixed relatively well in that part of the container intowhich the blow-off steam is introduced. This ensures that a heatexchanger which is provided in the container can recover heat from thesteam relatively efficiently, since there are hardly any temperaturegradients in that part of the container. In addition, the tangentialintroduction, if desired in combination with the radial introduction,ensures that the remaining portion of the blow-off steam charge which isalready present is displaced in the direction of the outlet.

It is possible for the supplied blow-off steam to comprise solidparticles. The solid particles may, for example, be peelings from thepeeled tuberous crops, such as potato peelings. The peelings may comeinto contact with a heat exchanger provided in the container. Thesupplied charge may be directed at the heat exchanger.

The precipitation of solid particles on the heat exchanger may result ina reduced transfer of heat between the steam and the heat exchanger, asa result of which less heat can be recovered. An embodiment of themethod comprises the further step of removing the solid particlesprecipitated in the container by means of a Cleaning-in-Place method.The Cleaning-in-Place method ensures that the device can be cleanedduring operation without having to be taken out of service. As theblow-off steam charge is supplied in such a manner that it is directedat the heat exchanger and the charge has a considerable velocity, ablow-cleaning effect is achieved, as it were.

The Cleaning-in-Place method may comprise the step of supplying water tothe heat-exchange element. Preferably, the water introduced into thecontainer is pressurized. In this way, the pressure of the water willensure that the solid particles stuck to the heat-exchange element comeloose, and are carried along further into the container. Thus, theheat-exchange element remains clean.

In an embodiment, the solid particles are discharged from the container.This may be effected, for example, by providing an opening in the bottomof the container. The solid particles which have come loose will,together with the supplied water and under the force of gravity, betaken to a receptacle below the container, in particular the bottom ofthe container, and will leave the container there. The opening in thebottom of the container also ensures that water of condensation canleave the container in a simple manner. The opening may therefore alsobe suitable for other purposes than a Cleaning-in-Place method.

It is possible for the Cleaning-in-Place method to comprise the step ofsupplying a blow-off steam charge. The relatively high pressure and therelatively high atmospheric humidity may lead to the stuck particlescoming loose and being carried along further in the container.Preferably, the steam is introduced in such a manner that a stream ofthe steam is directed at the heat-exchange element.

According to an aspect of the invention, a device is provided forrecovering heat from intermittently and instantaneously releasedblow-off steam charges. The device may form part of an assembly forpeeling tuberous products, such as potatoes, with the assemblyfurthermore comprising a steam bulb, wherein an outlet of the steam bulbis connected to an inlet of the device.

The device according to the invention comprises a container with aninternal volume. The container may be a hat-like container. Thecontainer may be provided with an inlet for introducing blow-off steaminto the container, with an outlet for discharging blow-off steam andwith a heat-exchange element for recovering energy (heat and/orcondensation energy) from the blow-off steam. In a position of use ofthe container, the heat-exchange element is above the outlet. The outletmay be configured to be open during the recovery of energy from theblow-off steam. In this way, it is possible to introduce air into thecontainer via the outlet during heat recovery. Thus, the outlet is notonly open when the blow-off steam charge is being discharged, but alsoduring the heat-recovery phase. The fact that the outlet is open meansthat air can be drawn in and thus can be introduced into the container.The air which is drawn in forms a barrier between the steam charge andthe discharge. Consequently, it is relatively difficult for the steamcharge to leave the container. In addition, the air which is drawn incauses the steam to be kept above the outlet, so that the steam isbrought into contact with the heat-exchange element.

By means of the device, it is possible to recover heat in a relativelycontinuous manner from an introduced blow-off steam charge. The blow-offsteam will tend to gather in a specific part of the container. Arelatively high position of the heat-exchange element compared to a lowposition of the outlet makes it possible for the relatively hot steam tobe kept in the container for longer, since the hot steam tends to flowupwards. The fact that the outlet is open ensures that air can be drawnin. The air keeps the steam in the vicinity of the heat-exchange elementand forms a barrier preventing steam from flowing out via the outlet.The relatively high position of the heat-exchange element also ensuresthat energy can be recovered from a blow-off steam charge for a longtime. After the energy from the blow-off steam has been recovered, inparticular by condensation, this portion will become relatively heavydue to this portion having a higher density than portions from whichenergy can still be recovered, and will therefore tend to movedownwards. The portion from which energy has been recovered and whichhas largely condensed, will be referred to as fluid below. Bypositioning the outlet below the heat-exchange element, use is made ofthe fact that cooling down results in an increase in density. In agravitational field, the heavier, cooled-down fluid will thereforesink/drop. The outlet is situated at a lower gravitational potential.After the heat recovery, the relatively heavy fluid will therefore flowin the direction of the outlet. In this way, a natural separation takesplace within a blow-off steam charge. In addition, the device accordingto the invention ensures that the relatively cold blow-off steam forms abuffer for the relatively hot blow-off steam, so that the hot blow-offsteam cannot flow out of the container.

Preferably, the heat exchanger is provided in the internal volume of thecontainer. With the known device, a condenser is placed in the internalvolume and a heat exchanger is placed outside the container. Thecondenser has to store as much heat as possible from the charge and amedium has to recover the heat from the condenser in order then totransport it to the heat exchanger, where the heat is transferred toanother medium. Thus, multiple steps are required in order to recoverthe heat. In the embodiment according to the invention, the heatexchanger is situated in the internal volume of the container and theheat from the steam can be transferred directly to the medium. Heatrecovery can thus be effected in only one step. This is partly madepossible by the fact that the blow-off steam charge can stay in thecontainer for a relatively long time. All in all, the losses arerelatively small, as a result of which a highly efficient device forrecovering heat is obtained.

Preferably, the internal volume comprises a buffer volume around theheat exchanger and a volume which is at least equal to the volume of thecharge. Thus, when the next charge is introduced, at least a volume ofthe size of the buffer volume remains behind in the internal volume. Thebuffer volume around the heat exchanger is where the most energy-richportion of the previous charge is situated and this remains behind andcould still be used for energy recovery. The other portions of theprevious charge are forced out.

In a preferred embodiment, the container comprises an entrance forsupplying relatively cold air, for example outside air. Said entrancemay be the outlet. The outlet may be an open connection to the outsideair or a further device which is situated downstream. As a result of theenergy recovery in the container, the volume of the steam will decrease.Cold air can be drawn in via the entrance/outlet. Preferably, thedrawing-in takes place via the outlet, as a result of which a blanket ofcold air is formed near said outlet, which blanket of cold air acts as akind of valve which blocks the discharge of hot steam via the outlet.

In an embodiment, the heat-exchange element is a heat exchanger.Preferably, the inlet is placed near the heat-exchange element, so thatthe heat losses are relatively small. The inlet is preferably positionedhigher than the outlet. Thus, fluid which leaves the container via theoutlet will not come into contact with supplied steam which would resultin a loss of energy.

Preferably, the inlet is provided in an upper part of the container. Therelatively hot steam tends to flow upwards. By providing the inlet in anupper part, the steam will be introduced into the container at its finalposition, thus rendering the heat losses relatively small.

It is possible to provide the inlet tangentially to a wall of thecontainer. In this way, a blow-off steam charge introduced into thecontainer will be provided with a rotating stream. The rotation ensuresthat the blow-off steam charge is mixed well, as a result of which thetemperature differences in the steam charge become relatively small.

It is possible for the container to be provided with a tube having afirst and a second nozzle orifice. The first nozzle orifice is providedin the internal volume of the container. The second nozzle orifice isplaced above the first nozzle orifice, and outside the internal volumeof the container. The outlet is formed by the first nozzle orifice. Thetube may, for example, be a pipe which extends upwards. The pipe isplaced such that steam can only leave the device via a highergravitational potential. This required bridging of the gravitationalpotential ensures that a natural barrier is formed for the steam toleave the device. Such an embodiment ensures that the blow-off steampresent in the container has to move from the outlet upwards in order toleave the container. The blow-off steam present at the outlet isrelatively heavy and tends to move downwards. Therefore, the blow-offsteam can only leave the container if sufficient energy is supplied tothe blow-off steam. This is possible, for example, by supplying a newblow-off steam charge. Supplying a new charge will displace the oldcharge and push it upwards from the outlet in the pipe. The tube willtherefore cause a barrier to be formed near the outlet, which preventsthe blow-off steam which is present in the container from flowing away.

Preferably, the outlet is placed at a vertical distance from a bottom ofthe container. Thus, a barrier volume is formed in the container. Inorder to leave the container, a blow-off steam charge which is presentin the container first has to flow down and then flow up.

The volume of the portion of the internal volume of the container whichis above the outlet may be greater than the volume of an amount ofblow-off steam to be introduced into the device. This prevents steamfrom already being lost when a steam charge is being supplied.

Preferably, the upper volume is adjusted using the volume of theblow-off steam charge. Relatively large blow-off steam charges willrequire a larger volume. Preferably, the volume of the portion above theoutlet is equal to 120% of the volume of the blow-off steam charge.

The steam inlet may be provided with an air-distributing element inorder to ensure that the blow-off steam flows evenly into the container.In this way, the blow-off steam can be introduced into the container ina controlled manner. In this case, relatively few pressure differencesoccur in the container itself, which benefits the service life of thedevice.

An embodiment of the present invention will be explained in more detailby means of a description of the figure. It should be clear to theperson skilled in the art that the illustrated embodiment in no waylimits the scope of protection which is defined in the claims. Theinvention is described with reference to a number of advantages. Each ofthese advantages may comprise a patentable invention. Implicitadvantages of specific embodiments will also be obvious to the personskilled in the art. Each of the implicit advantages can also form abasis for a patentable invention according to the application oraccording to a divisional application. In the figures:

FIG. 1 shows a cross-sectional side view of a device according to anembodiment of the present invention;

FIG. 2 shows a cross-sectional top view of the device shown in FIG. 1;

FIGS. 3 a and 3 b show a cross-sectional side view of an embodiment ofthe device just after the supply of a blow-off steam charge, and justbefore the supply of a blow-off steam charge.

FIG. 1 shows a steam condenser 1. The steam condenser 1 comprises avessel 6 with an internal volume. The vessel 6 is provided with an inlet7 for supplying blow-off steam S_(H) to the vessel 6. The inlet 7 isplaced near a top side of the vessel 6 and ends in a part of the vessel20 in which a heat exchanger 9 is placed. The heat exchanger 9 comprisesa supply line 16 for liquid and a discharge line 15 for liquid. Thesupply line 16 is connected to a number of tubular spirals 14, which aresituated in the internal volume of the vessel 6. Furthermore, a tube 8with an internal duct 3 is placed in the vessel 6. The duct forms aconnection to an exit 5 which is provided on an upper side of the vessel6. The central tube 8 with the duct 3 forms a discharge 10 for thevessel 6. The vessel 6 is placed on a frame 4. At a bottom side of thevessel 6, a cone-shaped bottom 30 with an opening 31 is provided. Theopening ends in a receptacle 33 placed inside the frame 4 for collectingcondensed water.

The operation of the steam condenser 1 illustrated in FIG. 1 is asfollows. A batch of blow-off steam S_(H) is introduced into the vesselvia the inlet 7. In this case, the blow-off steam may come from apotato-peeling machine or a steam bulb, although the invention is notlimited thereto. In such a case, it is possible for a relatively largeamount of blow-off steam to be released in a relatively short time, suchas for example 2 to 3 seconds. The release may take place relativelybatchwise, that is to say that in such a case, no continuous stream ofblow-off steam is introduced into the vessel 6, but that the steam issupplied intermittently. If a potato-peeling machine is connected to theinlet, the period during which no steam is supplied may be approximately60-70 seconds.

The supplied blow-off steam will flow into the vessel 6 and in this casetake up a certain amount of the internal volume of the vessel 6. Abottom layer of the steam present in the vessel is indicated by line II.The steam has a relatively low density, also with respect to hot air,and will therefore gather at the top of the vessel 6. Preferably, thevessel 6 is dimensioned such that, after the amount of steam hasentered, the bottom layer H of steam is just above the discharge 10 ofthe tube 8.

The blow-off steam introduced into the vessel will, at the top side ofthe vessel, come into contact with the heat exchanger 9. A relativelycold liquid is supplied in the supply line 16. Preferably, water isused. The water preferably has an inlet temperature of approximately 80°C. The cold water flows from the supply line 16 to the various spirals14. In the spirals, the heat exchange between the relatively hot steamand the relatively cold liquid will take place. In particular,condensation of the steam will take place there.

In the process, the heat exchange medium/the liquid heats up. The liquidwill flow further in the direction of the discharge line 15 of the heatexchanger 9. The water coming from the discharge line 15 may in thiscase have a temperature of approximately 95° C. The water may then beused for applications which require relatively hot water by connectingthe discharge line 15 to another device, as desired. However, it ispossible to choose other liquids for use in the heat exchanger. It isalso possible to use other inlet temperatures for the cooling liquid, sothat a different outlet temperature associated therewith is obtained.Other embodiments of the heat exchanger are also conceivable.

The steam will give off part of its heat to the relatively cold heatexchanger 9, so that the steam cools down and its density increases. Inparticular, the steam will give off its heat through condensation.Consequently, the cooled-down steam and in particular the condensateformed by condensation will move downwards/drop into the vessel. At thebottom of the vessel, the condensate and the relatively cold steam willcollect. Due to the phase change from steam to condensate, the volume ofthe steam will decrease, as a result of which the bottom layer of thevolume of the steam moves upwards in the direction of line I.

When a new blow-off steam charge is supplied to the vessel 6, thesupplied new charge will displace the remaining steam from the previouscharge in the direction of the discharge 10. The bottom layer will thenmove down by height H, from line I in the direction of line II. Thenewly supplied charge again comes into contact with the heat exchanger9, as a result of which the exchange of heat with the steam can takeplace again. In this way, continuous heat exchange with discretelysupplied blow-off steam becomes possible.

The condensate of the steam, water, will collect at the lower side ofthe vessel 6. The conically shaped bottom 30 of the vessel 6 will causethe water to flow in the direction of the opening 31 and to be collectedin a receptacle 33. The water of condensation 32 collected here can thenbe used further for heat recovery. Also, solid particles which have beencarried along in the charge can be discharged via the opening 31.

Preferably, the device is dimensioned such that the boundary layer II ismoved up by a height H. In this case, the device 1 may be dimensionedsuch that the boundary layer I is always situated below the heatexchanger. As a result thereof, steam is always in contact with the heatexchanger. Preferably, a new steam charge is introduced when theboundary layer II reaches the lower side of the heat exchanger, or justbefore that point in time.

FIG. 2 shows a top view of the device 1 shown in FIG. 1. Identical partshave been given the same reference numerals in this figure which showsthe vessel 6 with an internal volume. In the internal volume, the tube 8is provided with a duct 3. The heat exchanger 9 is placed around thetube 8. The heat exchanger 9 comprises a supply line 16 and a dischargeline 15 for liquid. The heat exchanger 9 is also provided with heatingspirals 14. The spirals are placed at a distance from the wall of thevessel 6 and along a circumference provided in the vessel 6. The inlet 7is provided in a side wall of the vessel 6. In the illustratedembodiment, the inlet 7 is provided tangentially in the container. Thisensures that rotation is imparted to the steam when it is introduced.This rotation ensures that the steam can be brought into intimatecontact with the heating spirals 14.

The general principle of the invention is explained with reference toFIGS. 3 a and 3 b. FIG. 3 a shows a device 101 with a container 106 justafter a blow-off steam charge has been supplied. The blow-off steamcharge is situated in the container 106 and takes up part of theinternal volume (indicated by number 120). In the container 106, aboundary of a steam/air layer II is present. Above the boundary of thesteam/air layer II, steam is present, and below the boundary, there isair. In this case, the steam level reaches just above the discharge 110.Since steam tends to move upwards, the steam will not be able to leavethe container 106 via the discharge 110. In this case, the air which ispresent near the discharge 110, which is relatively heavy and thereforedoes not tend to move upwards, also forms a barrier for the steam layerto leave the device 101 via the outlet 110. The heat of the steam andthe condensation energy are absorbed by means of a heat exchanger whichis not illustrated and is provided in a top part of the container 106.It will be clear to the person skilled in the art that this may beeffected in many ways. Due to the condensed portion, the volume of thesteam will significantly decrease. Consequently, for example, air may bedrawn in, for example via the outlet 10.

This results in the steam/air layer moving upwards, in the direction ofthe heat exchanger. The situation just before a blow-off steam charge isintroduced is illustrated in FIG. 3 b. This shows that the volume ofsteam (denoted by reference numeral 120) is reduced. Consequently, thevolume of air (indicated by reference numeral 121) has increased.Preferably, the device 101 is designed and dimensioned such that, justbefore a new steam charge is supplied, the steam/air layer I is situatedjust below the heat exchanger, so that the heat exchanger issubstantially in contact with the volume of steam 120. As a resultthereof, it is possible to exchange heat in a relatively continuousmanner using intermittently and instantaneously supplied blow-off steamcharges.

To the person skilled in the art, it will be clear that FIG. 3 a andFIG. 3 b show a diagrammatic view of the processes of the method and inthe device according to the invention. These figures are therefore notintended to be interpreted as limiting, but only serve to explain thepresent invention. Thus, in practice, it is for example possible for thetransition between the steam layer and air layer present in thecontainer to be gradual. Nevertheless, it will be possible to indicatewhere there is a boundary between steam and air, and in such a case, itwill be possible to use the insights of the present invention.

It will be clear to the person skilled in the art that the presentinvention is not limited to that which has been described here, and thatseveral equivalent embodiments of the invention are possible.

1. A method of recovering heat from intermittently and instantaneouslyreleased blow-off steam charges, wherein the method is carried out usinga container with an internal volume, provided with an inlet and anoutlet, wherein the method comprises the following steps: supplying tothe container via the inlet and collecting in the internal volume of thecontainer a blow-off steam charge (S_(h)), wherein the charge is held ina gravitational field; recovering energy from a portion of the blow-offsteam charge (S_(h)) by condensation thereof, wherein condensationresults in a stream from said portion to an outlet which is at a lowergravitational potential; discharging a portion of the charge from theinternal volume of the container via the outlet at a lower gravitationalpotential by supplying a subsequent blow-off steam charge (S_(h)) to theinternal volume and thus expelling the charge which is present via theoutlet; drawing in air via the outlet during heat recovery.
 2. Themethod according to claim 1, wherein the volume of the supplied blow-offsteam charge (S_(h)) is smaller than the volume of the container whichis at a higher gravitational potential than the outlet.
 3. The methodaccording to claim 2, wherein the volume of the supplied blow-off steamcharge (S_(h)) is between 70% and 90% of the internal volume of thecontainer.
 4. The method according to claim 1, wherein the step ofexchanging heat from the blow-off steam charge at least partly coincideswith the step of supplying the next blow-off steam charge.
 5. The methodaccording to claim 1, wherein the step of recovering heat from theblow-off steam comprises bringing the blow-off steam into contact with aheat exchanger provided in the container.
 6. The method according toclaim 5, wherein a steam/air layer is formed in the container, whereinthe steam is at a higher gravitational potential than the air, andwherein the energy recovery takes place by condensation at said highergravitational potential.
 7. The method according to claim 6, wherein,after the introduction of a blow-off steam charge, the steam/air layeris at a vertical distance from the heat exchanger, and wherein thesteam/air layer is at a smaller vertical distance just before the stepof supplying the next charge, wherein a height difference between thesteam/air layer after the introduction and before the supply correspondsto a buffer volume of blow-off steam in the container.
 8. The methodaccording to claim 7, wherein recovering heat takes place in aheat-exchanging volume, wherein the heat-exchanging volume is between10% and 30% of the volume of the blow-off steam charge, and wherein theremaining portion of the blow-off steam charge forms the buffer volume.9. The method according to claim 1, wherein the blow-off steam issupplied at a top side of the container, and wherein the blow-off steamis discharged via a bottom side of the container.
 10. The methodaccording to claim 1, wherein the supply of blow-off steam takes placeduring a first time period, and wherein heat recovery from the blow-offsteam takes place during a second time period, wherein the first timeperiod is less than 10% of the second time period.
 11. The methodaccording to claim 1, wherein the supply of blow-off steam takes placeindependently from the heat recovery.
 12. The method according to claim1, wherein the method comprises providing a substantially instantaneousand intermittent blow-off steam charge.
 13. The method according toclaim 1, wherein the blow-off steam is supplied to the internal volumein a tangential direction.
 14. The method according to claim 1, whereinthe supplied blow-off steam is directed at the heat exchange zone.
 15. Adevice which recovers energy from intermittently and instantaneouslyreleased blow-off steam charges (S_(h)), comprising a container with aninternal volume, wherein the container is provided with an inlet whichintroduces blow-off steam (S_(h)) into the container, with an outletwhich discharges blow-off steam, and with a heat-exchange element whichrecovers energy from the blow-off steam, wherein the heat-exchangeelement, in a position of use of the container, is placed at a verticaldistance above the outlet, wherein the outlet is configured to be openduring the recovery of energy from the blow-off steam in order tointroduce air via the outlet during heat recovery.
 16. A deviceaccording to claim 15, wherein the heat-exchange element comprises aheat exchanger which is provided in the internal volume of thecontainer.
 17. A device according to claim 15, wherein the inlet isplaced near the heat-exchange element.
 18. A device according to claim15, wherein the container comprises an inlet for drawing in a gas, suchas air.
 19. A device according to claim 18, wherein the inlet and theoutlet are the same.
 20. A device according to claim 15, wherein theinlet is provided in an upper part of the container.
 21. A deviceaccording to claim 15, wherein the inlet is provided tangentially to awall of the container.
 22. A device according to claim 15, wherein thecontainer is provided with a tube having a first and a second nozzleorifice, wherein the first nozzle orifice is provided in the internalvolume of the container, and wherein the second nozzle orifice is placedat a vertical distance above the first nozzle orifice and outside theinternal volume of the container, and wherein the outlet comprises thefirst nozzle orifice.
 23. A device according to claim 15, wherein theoutlet is placed at a vertical distance from a bottom of the container.24. A device according to claim 15, wherein the inlet is provided withan air-distributing element in order that the blow-off steam flowsevenly into the container.
 25. An assembly comprising a steam-peelingdevice and a device according to claim 15 connected to the steam-peelingdevice.